The field of the present disclosure relates generally to analysis and monitoring of defects and fatigue in structures. More particularly, the present disclosure relates to systems and methods for fatigue detection utilizing exoelectron emission.
Typically, analysis and monitoring of defects and fatigue detection require that a physical crack or defect occur in the structure before a detection occurs. For example, techniques such as dye penetrants, acoustic, ultrasound, Eddy current and X-ray detection require that a physical crack or defect be present in a structure before such techniques allow for detection of a defect or fatigue in the structure. Such techniques thus do not allow for early detection of defects or fatigue before a defect or crack is already present.
Further, typically dye penetrating methods are very limited in resolution and accuracy, as cracks need to exist on the surface and be observable to the naked eye or under magnification to be detectable. Other techniques, such as acoustic, ultrasound and Eddy current X-ray techniques may provide higher resolution than dye penetrants, but the detection time can be long as multiple images must be analyzed and the costs can be high.
Exoemissions, as used herein, refers to the phenomenon of emission of charged particles (e.g., electrons) from solid surfaces after plastic deformation, stress, strain, abrasion or particle bombardment of the solid surface. Exoemissions are emitted at relatively low temperatures and at a rate that decreases with time. Typically, detection of exoelectrons has only been in systems under high vacuum (i.e., <10−7 Torr) conditions, which has prevented exoelectron detection from being used for defect detection.